| 摘要 |
PROBLEM TO BE SOLVED: To obtain a duct structure hardly collapsed by thermal expansion by assembling bricks having fan-shaped or wedge-shaped cross-sections in the circumferential direction so that the cross section shape of the duct may be radially separated by a plurality of bricks to form the duct in which a molten glass at high temperature passes through. SOLUTION: This duct structure is usable in a vacuum housing of a defoaming apparatus with a reduced pressure. For example, when the vacuum housing has a portal shape, a lifting pipe (the duct) is installed in the left end part of a defoaming vessel with the reducing pressure, and a lowering pipe (the duct) is installed in the right end part. The lifting and lowering pipes have the same structure. The duct structure is constituted of rows of twelve bricks 30, 30... assembled in circumferential direction, and the number of the bricks is not limited to the number. The bricks 30, 30... in the lifting pipe 16 are formed into wedge shapes, and stuck in the circumferential direction to provide a molten glass passage 32 having a circular cross section. Tabular refractory bricks (sealing members) 36 for blocking joint parts 34 are fixed to the joint parts 34 to prevent the leak of the molten glass.
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